What is the difference between Behaviour Driven Development (BDD) and Acceptance Test Driven Development (ATDD)?

I'm writing a short paper to expound the benefits of unit testing and TDD. I've included a short section at the end entitled "Beyond TDD" in which I'd hoped to cover a few different approaches based on TDD, BDD and ATDD in particular.

I'm sort of familiar with BDD (I've played with SpecFlow) but after reading up on ATDD, it sounds very similar. Are BDD and ATDD just two names for what is essentially the same process - document the behaviours in a 'ubiquitous' language', generate an automated acceptance test suite, then go about making the acceptance tests pass?